Ecological Studies of Benthic Macroinvertebrates for Determining Sedimentation Impacts In
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Ecological studies of benthic macroinvertebrates for determining sedimentation impacts in Chattahoochee National Forest streams Scott D. Longing Dissertation submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY In Entomology J. Reese Voshell, Jr. E. Fred Benfield C. Andrew Dolloff Richard D. Fell Scott M. Salom April 7th, 2006 Blacksburg, Virginia Keywords: sedimentation, benthic macroinvertebrates, bioassessment, biological monitoring Chattahoochee National Forest, Chattooga River watershed © 2006 Scott D. Longing Ecological studies of benthic macroinvertebrates for determining sedimentation impacts in Chattahoochee National Forest streams Scott D. Longing ABSTRACT Understanding sedimentation impacts to benthic macroinvertebrates in headwater, mountain streams is a top priority of watershed management programs in the Chattahoochee National Forest. Five studies involving the analysis of historical, biological survey data and current data were conducted to improve our understanding of macroinvertebrate response to sedimentation and to support the development of biological information for sediment load models to be applied in the Chattooga River watershed. An initial analysis of historical data involving a composited, macroinvertebrate reach-scale sample revealed weak relationships between assemblage metrics and sedimentation, which was similar to results of two recent macroinvertebrate studies that found biological ratings of good or excellent with reported physical impact attributed to sedimentation. Those findings and field reconnaissance in the Chattooga River watershed revealed that patchy, coarse sands may be the primary issue of concern regarding sedimentation impact to benthic macroinvertebrates. Therefore, a modified sampling approach was used to investigate relationships of macroinvertebrates and environmental conditions that included micro-habitat patches containing coarse sands, a product of erosion associated with Southern Blue Ridge, silicate parent geology. At the microhabitat, patch scale, flow velocity was the main environmental factor associated with a macroinvertebrate assemblage gradient, and was significantly correlated with percent deposited sediment across 264 samples. The high dominance of just a few macroinvertebrate genera, and the majority lack of individual macroinvertebrate associations with dominant substrate types may suggest that the dominant macroinvertebrates utilize a multi-microhabitat portion of the streambed at any given time, which may be due to the homogenization of streambeds due to sand (providing ease of movement) and its immobility (low bedload volume and sand patch shift). Because flow was the only significantly correlated environmental variable on an assemblage gradient produced by ordination (and was individually correlated with dominant substrate and percent deposited sediment), a subsequent study was conducted to determine macroinvertebrate sensitivity to deposited sediments among two flow-differentiated habitat types. Results showed that more taxa were related to a gradient of percent deposited sediment in fast water habitats, and no taxa were positively correlated with percent deposited sediment. Indicator species analysis found a number of taxa that were associated with a four-level grouping of percent deposited sediment levels. Therefore, a final study involved calculating deposited sediment tolerance values using indicator species associations and individual cumulative abundances across percent deposited sediment levels. The final index developed from cumulative abundances showed a relationship with deposited sediment within the range 0 – 30%, and that low range was due to the low deposited sediment levels at which all 50% cumulative abundances fell (1 - 10%). The sedimentation index produced from indicator species analysis produced a reach-scale index that was related to percent pool embeddedness. Key findings from these studies are: (1) sand is the primary deposited sediment type, with most streambed comprised of cobble-sand substrate, (2) few taxa are associated with deposited sand substrate, (3) there are high numbers of a relatively few dominant taxa across samples and streams, (4) macroinvertebrate response to deposited sediments is greatest in fast water habitats, and (5) the developed sedimentation biotic index is a potential, assemblage-level indicator of increasing sedimentation in these headwater systems. The functional and habit organization of the four most dominant taxa determined in recent studies suggest that they may be utilizing sand patches for crawling and collecting food, therefore structurally adapting to long-term, press disturbances due to historical and contemporary anthropogenic activities and natural erosion. In addition, macroinvertebrate assemblage composition in these streams indicates overall good “health” and suggests streambed stability in the presence of a large portion of coarse sand. However, an important question that remains involves sand movement along streambeds and the ecological consequences of continued sediment inputs to these headwater systems. In loving dedication to my parents, Ernie and Vicki Longing, to Elly and Hannah, and to the memory of C.D. (Pap) Longing. iv Acknowledgements A very special thanks to Dr. J. Reese Voshell, Jr. He gave me an opportunity of a lifetime in being a part of his aquatic entomology lab and I can only hope to one day practice the guidance and mentorship that he showed me. Most of all, through his thoughtful direction and friendship I persevered through graduate school during some tough years. My two very special lab-mates, Stephen Hiner and Dr. Amy Braccia, always made me laugh and never were bothered to give a helping hand for anything. Stephen inspired me to never get mad at anything and to always have a plan. When I arrived on campus, Dr. Michael Moeykens was especially helpful in getting me situated. I appreciate Dr. C. Dayton Steelman at the University of Arkansas for helping me get started and going on this graduate school road. I thank my Ph.D. graduate committee, Drs. E. Fred Benfield, C. Andrew Dolloff, Richard D. Fell, and Scott M. Salom for their support and providing time and advice for a rookie scientist. A special thanks to Dr. Dolloff for providing research support through the USFS Coldwater Fisheries Research Unit and for introducing me to northern Georgia. The support and help in the field of Craig Roghair, Jon Moran, and Dan Nuckols of the USFS Center for Aquatic Technology Transfer were much appreciated. Charlene Breeden of the USFS Tallulah Ranger District in Georgia provided valuable advice and resources while working in the Chattahoochee National Forest. The effort of Jamie Roberts is greatly appreciated as he came through in crunch-time by providing a helping hand during tough, north Georgia fieldwork. I am very grateful to several people who processed numerous macroinvertebrate samples: Trisha Voshell, Amanda Ellis, Rachel Wade, Kathy Hannah, and Hillery Warner. I greatly appreciate the kindness of the entire faculty and staff of the Virginia Tech Department of Entomology, some who helped with scholastic endeavors and some who just listened and offered good advice, and friendship most of all. Some very special people helped me through some tough times and I’ll never forget their kindness. Dr. Ksenia Tcheslavskaia was a precious shoulder to lean on. I am also very grateful to Dr. Ashley Lamb for her kindness and for always offering a helping hand during some intense months of writing. A special thanks to Brian Eisenbeck for helping me outlast winter 2006 at the farm. I v thank Dwight Paulette for allowing me to live on Kentland Farm; saying that living there made life more enjoyable and much easier is an understatement. I thank two of the sweetest ladies in the world, Ann Germano and Elly Mildred Mead, for always supporting me and making family so special. I give dearest thanks and appreciation to my parents, Ernie and Vicki Longing, and my two sweet sisters, Amy and Sarah. Only through their never-ending love and support was I able to make it to where I am today. Finally, I acknowledge the two dearest little rascals in my life, Elly and Hannah. During the toughest times, I could always count on the love in my heart and thoughts of them to make me smile. vi TABLE OF CONTENTS ABSTRACT……………………………………………………………………………………………… ii AKNOWLEDGEMENTS ………………………………………………………………………………. v TABLE OF CONTENTS……………………………………………………………………………….. vii LIST OF TABLES……………………………………………………………………………………… ix LIST OF FIGURES…………………………………………………………………............................... x INTRODUCTION………………………………………………………………………………………. 1 Literature cited…………………………………………………………………………………. 8 CHAPTER 1: Relationships of sedimentation and benthic macroinvertebrate assemblages in Southern Ridge streams as determined by systematic longitudinal sampling at the reach scale..………………… 14 Introduction……………………………………………………………………………………. 16 Methods………………………………………………………………………………………... 17 Results……………………………………………………………………………………......... 21 Discussion……………………………………………………………………………………... 23 Literature cited………………………………………………………………………………… 28 Tables…………………………………………………………………………………………. 31 Figures……………………………………………………………………………………….... 36 CHAPTER 2: Stream size, reach- and segment-scale environmental factors influencing benthic macroinvertebrates in Chattahoochee National Forest streams……………………………………….... 39 Introduction……………………………………………………………………………………